The use of high-power fiber-coupled lasers continues to gain popularity for a variety of applications, such as materials processing, cutting, welding, and/or additive manufacturing. These lasers include, for example, fiber lasers, disk lasers, diode lasers, diode-pumped solid state lasers, and lamp-pumped solid state lasers. In these systems, optical power is delivered from the laser to a work piece via an optical fiber.
Various fiber-coupled laser materials processing tasks require different beam characteristics (e.g., spatial profiles and/or divergence profiles). For example, cutting thick metal and welding generally require a larger spot size than cutting thin metal. Ideally, the laser beam properties would be adjustable to enable optimized processing for these different tasks. Conventionally, users have two choices: (1) Employ a laser system with fixed beam characteristics that can be used for different tasks but is not optimal for most of them (i.e., a compromise between performance and flexibility); or (2) Purchase a laser system or accessories that offer variable beam characteristics but that add significant cost, size, weight, complexity, and perhaps performance degradation (e.g., optical loss) or reliability degradation (e.g., reduced robustness or up-time). Currently available laser systems capable of varying beam characteristics require the use of free-space optics or other complex and expensive add-on mechanisms (e.g., zoom lenses, mirrors, translatable or motorized lenses, combiners, etc.) in order to vary beam characteristics. No solution exists that provides the desired adjustability in beam characteristics that minimizes or eliminates reliance on the use of free-space optics or other extra components that add significant penalties in terms of cost, complexity, performance, and/or reliability. What is needed is an in-fiber apparatus for providing varying beam characteristics that does not require or minimizes the use of free-space optics and that can avoid significant cost, complexity, performance tradeoffs, and/or reliability degradation.
Broad area laser heating applications can include hardening, annealing, heat treating, cladding, tape laying, brazing, soldering, and welding for plastics, semiconductors, glasses, and metals. These large area heating applications usually require beam shapes that are rectangular or square and larger in area than a 3 mm diameter circular. Rectangular laser beams shapes are typically produced by a stack of diode bars, square core delivery fibers, or purpose-built beam shaping optics. These methods produce fixed dimensions or aspect ratios of the beam shape that are not easily adjusted to change the heating width or area. The heating width requirements can be different for different product designs or changing for different features within one product design.
To accommodate the different heating width requirements, users must change the optical configuration of the laser heating tool or they must produce multiple adjacent heating tracks to achieve the desired heat track width. Both options increase the cycle time and reduce return on investment. One alternative method to produce different heating track widths is to use a “zoom” optic assembly that enables variable magnification in one or both axes of the rectangular beam shape. These zoom optics are expensive and not feasible for every application due to the weight and size of the assembly.
Therefore, methods for controlling properties of lasers, while overcoming the limitations of conventional processes and systems, to provide improved articles would be a welcome addition to the art.